A fracturing stack, often simply referred to as a “frac stack,” is a device used at the well head to transfer pressurized fluid downhole. The pressurized fluid fractures the subterranean strata, thereby releasing gas trapped in that strata and facilitating the recovery of otherwise unreachable gas. Oftentimes, after a frac stack has been used, it is left at the wellhead until permanent recovery equipment can be set up to replace the frac stack, at which point the well becomes “live.” During the course of normal recovery operations, a frac stack may remain at the wellhead for a period of several days or even several months before the permanent recovery equipment is put into place.
After the well is fractured and before the well becomes live, the frac stack is used to seal the well at the wellhead through a series of valves. As the various valves are closed, a mixture of gas and water remains trapped there between.
Notably, when gas is trapped within the frac stack or frac tree, it is under tremendous pressure. Often times, for example, the gas may be compressed from a 3 inch pipeline to a ¾ inch pipeline. Under these conditions, the gas can freeze at temperatures as high as 52 degrees Fahrenheit. If gas trapped within the frac stack becomes frozen, the results can be devastating for a well operator. Consider the case where a well operator initiates permanent production of a well, i.e., makes a well live. In that case, the well operator must dedicate a team of individuals and thousands of dollars worth of equipment to that well. If the gas is frozen, the valves of the frac stack cannot open, gas cannot freely flow and, thus, the well cannot produce. At that point, between manpower, equipment, and the lost production of gas, the operator is losing tens of thousands of dollars per hour. Put simply, such a result cannot be tolerated.
Currently, well operators maintain frac stacks above a freezing point using rudimentary means. Commonly, a well operator will place flood lights or a portable heater around the frac stack and cover the set up with a tarp. The flood lights or portable heater must be powered by a portable generator. Such a scheme is undesirable because it requires the transport of several materials to remote job sites, the use of gas or diesel, and regular maintenance by individuals. Accordingly, this process is relatively expensive in terms of materials and manpower requirements.